Oxalic acid salt of a phenylene diamine



Patented Mar. 24, 1953 UNITED STATES OFFICE 2,632,770 OXALIC ACID SALT OF A-'PHENYLENE V DIAMINE Byron AfHunter, Oxford, Gonmyassign'or to United States Rubber company, New York, N. Y.-, a corporation of New Jersey 'NoDrawing. Original application January IS,

1949, Serial N0.

71,550, new Patent No.

anti-cracking agents.

.'2,605,250,jdat'e'd July 2'9, 1952, Divided and this application August 24, 1951; serial No.

- 1=Claim. (01. 260 -501) now U. S. Patent No. 2,605,250, issued July .29,

One =01 the :major rubber chemical :problems is the protection of rubber (natural and synthetic) against cracking due to weathering intyl-p-phenylene diamine.

diamine parts are by weight:

cool for about 2 hours. pension is filtered on a Buchner funnel, spread out on paper sheets and exposed to the air overnight. Yield=767 grams of white crystals (82% of theory). "The 'niaterialmelts at 170-171 "C. The product was analyzed. andioim'd'to'contain 8.77% nitrogen. The calculated value Sior C H: CH:

is 9.03% nitrogen.

volving either static or dynamic stress while sub- .jected to the influences of air '(oxygen; ozone), The same product can-also beobtainetl using 'heat'and/or light (sunlight). water rather than alcohol as "the-reaction me- .An object 'of-thisinvention is to provide chemdium. i m found useful 9 EXAMPLE 2.RUBBER TEsTs stantially :obviate such cracking tendencies. --A .15 p H I y furthe Object 11 provide y h m which, In order to illustrate the efiectiveness of NET- besides being a highly 'e'ifective anti-cracking (ii-Secondary yl p -p y dia n monoagent, will be considerably less toxic than other oxalate as an t -c cal in T-ubb'er otheruobjects 11 1 1 the following testing data-are'given: 1 mm the Pereinaft'er i I. m GR-S (rubbery 1,3-butadiene-styrene- (Such a relatively non-toxic chemical is the copozymer) mono-oxalic acid salt of N,N'-di-secondary bu- V I Synthet1c rubber compositions were .made up inaccordance with the following recipe: CH\BH H H H 00011 O Iii-(503. Stock Stock a 1' In This salt uniquely is --less toxic than N,N'-di- G155 .1000; i000 secondary butyl-p-phenylene diamine which i l (though-effective as an anti-cracking agent) :is 1 o toxic as to prohibit its commercial use. In g fig g g g spite of the relative limited dilution with the iviercabibtfiiitiiti' Heiiitii. 110' "15'0 oxalic acid, the mono salt retains high efiectivefl' iggi ggg butyipphcnyl'ene amine Z 1 5 ness as an anti-cracking agent. The dioxalic acid salt of N,N'-di-secondary butyl-p-phenylene The ingredients were combined on a rubber mill CH3 CH3 in the ordinary way and portions of each stock g 1 were cured at 45 pounds steam pressure for 90 O minutes. Samples of the cured stocks (1 x 4") were bent double and the ends fastened together 15 of no fi q an g chegncal' nd 40 and mounted on a board. The samples were t i f0 ownflg g' fi f i f fg fi gi then exposed to outdoor weathering conditions es are gwen o 1 e for 3 months. The samples were observed every second day for evidence of cracks. Using an EXAMPLE 1.PREPAR T 0F N,N'-DI-SE00NDARY arbitrary scale of visual crack rating, based on BUTYL-p-PHENYLENE DIAMINE MONO-()XALATE a large number of similar tests, stocks A and 2.70 grams (3 moles) of anhydrous oxalic acid 3 were rated as follows: are dissolved in 1500 cc. of ethanol (95%) (with slight warming to hasten solution). Into this Days, Days) solution, with stirring, are poured 666 grams e e i Degelop (3 moles) of N,N'-di-secondary butyl-p-phenylf j i ene diamine. The mixture is kept warm (50 C.) for 30 minutes and is then allowed to stand and s ck A 4 7 The thick, purple sus- StockB 39 7 3 EXAMPLE 3 In order to demonstrate the effectiveness of N,N'-di-secondary butyl-p-phenylene diamine mono-oxalate in retarding outdoor dynamic cracking of GR-S, portions of stocks A and B were cured for 90 minutes (1" x 6" Demattia grooved bending samples) and subjected to repeated bending on an outdoor bending machine. The samples were exposed to outdoor weathering conditions for 3 months. The machine was operated for approximately 16 hours per day at the rate of 10.5 kilocycles per day. The samples were observed periodically and rated according to an arbitrary visual rating scale based on observations of a large number of similar tests. The data obtained, as shown below, clearly illustrates the superior properties of the new anti-cracking chemical.

* Stock Stock Kilocyclcs flexing to very very slight cracks 271 4, 662 'Kilocycles flexing to very slight cracks 456 4, 760 Kilocycles flexing to slight cracks 533 5, 434 Kilocyclcs flexing to cracks 738 6, 731

EXAMPLE 4 II. In natural rubber Natural rubber compounds were made up according to the following recipe:

Stock Stock C D Smoked sheets 100. 100.0 Carbon black 45. 0 45. 0 Zinc oxide 5.0 5.0 Zinc soap of coconut oil acids. 3. 5 3. 5 Pine tar 3. 5 3. 5 Sulfur 3.0 3.0 Mercaptobenzothiazol 1.0 1.0 N ,N-di-secondary butyl-p-phenylene diamine mono-oxalate l. 5

4 EXAMPLE 5 Portions of stocks C and D were cured at 30 pounds steam pressure for minutes (1" x 6" Demattia grooved bending samples) and the resulting test pieces were repeatedly flexed on an outdoor bending machine as in Example 3. Stock C exhibited bad cracks after 233 kiloycyles of flexing whereas stock D, containing the new anticracking chemical, showed a similar degree of cracking after 1207 kilocycles.

The proportions, by weight, of the anti-cracking chemical may vary from 0.1% to 5%, based on the rubber content, although either smaller or greater proportions may be found useful.

It is understood that other desired filling and compounding ingredients may be incorporated along with the anti-cracking chemical. For example, there may be incorporated other accelerators, softeners, etc.

The anti-cracking chemical may be incorporated in any type of rubber composition, such as those used for automobile tires and tubes, hose, belting, sheet and thread rubber, rubberized fabrics, molded goods, boots and shoes, etc., whether vulcanized in a mold, in open steam, in hot air, or in the cold by the so-called acid process. If the material to which the anti-cracking chemical is added is a liquid such as rubber cement or an oil, it may be dissolved therein in a suitable small proportion. The anti-cracking chemical may be incorporated into solid substances by milling or mastication, and prepared for incorporation in dispersions or solutions either in powder, paste, or solution form, or applied in such forms for incorporation by diffusion to the surface of vulcanized or unvulcanized rubber goods.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

As a new chemical the mono-oxalic acid salt of N,N-di-secondary butyl-p-phenylene diamine.

BYRON A. HUNTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,875,903 Williams et a1 Sept. 6, 1932 2,067,686 Semon Jan. 12, 1937 2,279,385 Brimer Apr. 14, 1942 

